This invention relates to leak detection and more particularly to in-pipe leak detection in which a sensor detects the local pressure gradient near a leak.
A lot of research around the world is being considered to develop technologies to detect water leaks in water distribution networks. Water leakage is typically in the range of 20 to 30% on average of the water transported across the water distribution networks [1]; it may reach 50% for old networks. Numbers in brackets refer to the references listed herewith. The contents of all of these references are incorporated herein by reference in their entirety. Current leak detection methods [1, 2] include acoustic leak noise correlators, surface listening devices, ground penetrating radars, infrared thermography, chemical tracing, monitoring the flow field, and others. These methods have many limitations when applied to actual water distribution networks. They can be expensive, time consuming, not accurate enough, have noise interference problems, depend on pipe material, and the pipe location must be known.
Acoustic and leak noise correlators [3, 4] are the widely used methods at the present time by water municipalities worldwide. These methods work well in metal pipes; however, the effectiveness of the method is doubtful with plastic pipes due to high signal attenuation, low frequency content, and the pronounced effect of fittings on the wave propagation. Recently, leak detection using inside pipe moving sensors, like Sahara and Smartball systems [5-7], is considered to overcome many shortcomings of the conventional acoustic leak detection devices. The motivation for venturing into this technique stems from the ability to survey long distance pipeline in a network, surveying portions of the network which may be logistically difficult to access by other techniques. The closeness of the sensor to the leak location may enable capturing clean signals so leak detection and localization becomes more independent of pipe material, pipe depth, soil type, background noise, and other environmental effects.